use AdventureWorks2008
GO

--DROP TABLE Sales.Customer_NoIndex
--DROP TABLE Sales.Customer_Index

--create table Customer_NoIndex && Customer_Index
SELECT *
INTO Sales.Customer_NoIndex
FROM Sales.Customer
 
SELECT *
INTO Sales.Customer_Index
FROM Sales.Customer
GO

CREATE INDEX Idx_Customer_Index_CustomerID ON Sales.Customer_Index(CustomerID)

--query
-- #1
SELECT CustomerID, PersonID
FROM Sales.Customer_NoIndex
WHERE CustomerID = 11001
-- #2
SELECT CustomerID, PersonID
FROM Sales.Customer_Index
WHERE CustomerID = 11001